1. Field of the Invention
The present invention relates to new polynucleotides deriving from the nucleotide sequence of the erythropoietin gene (EPO) and comprising new SNPs, new polypeptides derived from the natural erythropoietin protein and comprising mutations caused by these SNPs as well as their therapeutic uses.
2. Related Art
The erythropoietin gene, hereinafter referred to as EPO, is described in the publication Jacobs K. et al. (1985) “Isolation and characterization of genomic and cDNA clones of human erythropoietin”; Nature 313 (6005), 806–810.
The nucleotide sequence of this gene is accessible under accession number X02158 in the GenBank database.
The erythropoietin protein is known to act on proliferation, differentiation, and maturation of progenitor cells of erythropoiesis. It determines their differentiation and maturation into erythrocytes.
EPO is also known to act as autocrine factor on certain erythroleukemic cells and to be a mitogen and a chemoattractant for endothelial cells.
EPO is also known to stimulate activated and differentiated B-cells and to enhance B-cell immunoglobulin production and proliferation.
EPO synthesis is subject to a complex control circuit which links kidney and bone marrow in a feedback loop. Synthesis depends on venous oxygen partial pressure and is increased under hypoxic conditions.
EPO production is influenced also by a variety of other humoral factors, such as testosterone, thyroid hormone, growth hormone, and catecholamines. In contrast, several cytokines such as IL-1, IL-6, and TNF-alpha, reduce EPO synthesis.
In the cell, binding of EPO to its receptor induces:
a release of membrane phospholipids,
the synthesis of diacyl glycerol,
an increase in intracellular calcium levels,
an increase in intracellular pH, and
an increase in intracellular phospholipase A2 and phospholipase C, the latter inducing fos and myc oncogenes.
Excess of EPO is known to lead to erythrocytosis. This is accompanied by an increase in blood viscosity and cardiac output and may lead also to heart failure and pulmonary hypertension. A significant reduction of platelets is also observed.
Thrombosis is another adverse effect of an excess of EPO.
Pulmonary and cerebral embolism, i.e. the sudden obliteration of a blood vessel by a clot or an extraneous compound transported by the blood, also constitutes a serious adverse effect related to EPO consumption.
However, when the amount of synthesized EPO is too low as it is in the case of severe kidney insufficiencies, anemias are often observed. Thus, EPO is often administered to patients with severe kidney insufficiency, with hematocrit below 0.3, in particular in dialysis patients.
The most important complication in the treatment with EPO is hypertony, the increases in urea, potassium, and phosphate levels, an increase in blood viscosity, an expansion of thrombopoietic progenitor cells and circulating platelets.
EPO is also used to activate erythropoiesis, allowing the collection of autologous donor blood.
Moreover, EPO use has been suggested also for non-renal forms of anemia induced, for example, by chronic infections, inflammatory processes, radiation therapy, and cytostatic drug treatment.
To a certain extent EPO is also a stimulating factor of megakaryocytopoiesis. The activity of EPO is synergized by IL-4.
EPO seems to possess neuroprotective capabilities since it has been demonstrated that EPO protects neurons against cell death induced by ischemia, probably by reducing free radicals production and by reducing oxidative stress effects.
It is known that the EPO gene is involved in different human disorders and/or diseases, such as different cancers like carcinomas, melanomas, myelomas, tumors, leukemia, and cancers of the liver, neck, head, and kidneys; cardiovascular diseases such as brain injury; metabolic diseases such as those not related to the immune system like obesity; infectious diseases, in particular viral infections such as Hepatitis B, Hepatitis C, and AIDS; pneumonia; ulcerative colitis; central nervous system diseases such as Alzheimer's disease, schizophrenia, and depression; tissue or organ graft rejection; wounds healing; anemia; allergy; asthma; multiple sclerosis; osteoporosis; psoriasis; rheumatoid arthritis; Crohn's disease; autoimmune diseases and disorders; genital or venereal warts; gastrointestinal disorders; and disorders related to treatments by chemotherapy.
The inventors have found new polypeptide and new polynucleotide analogs to the EPO gene capable of having a different functionality from the natural wild-type EPO protein.
These new polypeptides and polynucleotides can notably be used to treat or prevent the disorders or diseases previously mentioned and avoid all or part of the disadvantages, which are tied to them.